| Electronics > Beginners |
| DSO Record Length |
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| james_s:
--- Quote from: rhb on April 14, 2019, 07:30:52 pm ---The RTM3104 is a $20K instrument with the options I wanted. I am still appalled by the FW update fiasco. R&S are selling their customers beta test machines. I kept quiet about it for a long time, but as they have never provided an explanation and documentation of a fix, I have decided it's time to call a spade a spade. The last time Rich responded, I got an "I'm not ignoring you, I'm busy" email. I've not gotten *any* replies since. Sadly I did not have the wit to save a screen shot of the <3% overshoot. But I've got plenty of shots showing the 10% overshoot and a long list of other bugs, all of which were verified by R&S. --- End quote --- It's the nature of much of the software industry now, enabled by the ease of providing software updates. Ship the minimum viable product and update it later, you might have one QA guy on a team of developers and rely mostly on automation and customer feedback for testing. The result is predictable, crap quality with new bugs appearing as often as fixes. |
| Apochrom:
Well, I'm very surprised. For a beginner and hobbyist with a small budget these DSO's from Rohde and Schwarz or from Keysight or lecroy are unattainable. Before I bought the Siglent I studied many reviews and videos about DSO's and followed many discussions in the forum before I decided for the Siglent 1202x-e. So I was astonished with how many firmware problems (and Siglent had a hardware problem with its predecessor) some DSO's from Siglent/Rigol and Owon went on sale. Through my research I knew, that especially the Siglent 1202x-e and the Rigol 1054z got some firmware updates in the meantime and most of the problems are probably fixed. Since I don't need four channels and I think it's good that you don't have to hack the Siglent to get all options and the full 200Mhz BW I finally decided for the Siglent. I thought, okay if you have to work professionally with the DSO's or have the necessary money, you better get a device of the renowned brands Keysight, LeCroy or Rohde and Schwarz. I wouldn't have thought that these brands also have such big FW problems and that these devices are brought to the market too early and not fully developed. Madness - somehow it destroys my dream image of these brands... regards, Jürgen |
| David Hess:
There are a couple of things which help to make up for such short record lengths. Peak detection, and then later DPO (digital phosphor oscilloscope) operation which produces a complete histogram, capture the input at the maximum sample rate at any sweep speed. Delayed sweep and delayed triggering allow moving the acquisition window to a later point (1) without compromising sample rate. Delta delayed sweep allows two separate delayed acquisition windows. Older SRAM based Tektronix DSOs actually had larger record lengths than 2.5 kSamples but their much faster CCD based instruments were always very limited in comparison and I think this carried over into their later designs because they knew how to make a usable DSO with a short record length. Their early RAM based DSOs like the 2230/2232 had 4 kSamples while their much faster CCD based 2440 series (2) had only 1kSamples. Later RAM based TDS DSOs might have 8 MSamples through an option which is a respectful even for now and CCD based TDS DSOs had only 15 kSamples in 1998. (1) Technically it is possible to move to an earlier point as well by phase locking to the trigger but the only oscilloscopes I know of which did this were some early sampling oscilloscopes where it is a big advantage for preserving their very high bandwidth. (2) The 2440 series is the only example I know of where a DSO supports delta delayed sweep and in a weird way, that feature sort of doubles its record length although that was not the intention. I suspect they included it exactly to make up for its short record length even for that time and it does do that in most cases. |
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